I love these words from Spurgeon on church planting:
We have never sought to hinder the uprising of other churches from our midst or in our neighborhood. It is with cheerfulness that we dismiss our twelves, our twenties, our fifties, to form other churches. We encourage our members to leave us to found other churches; nay, we seek to persuade them to do it. We ask them to scatter throughout the land to become the goodly seed which God shall bless. I believe that so long as we do this we shall prosper. I have marked other churches that have adopted the other way, and they have not succeeded.